Ireland must "build relationships" with Donald Trump's key decision makers if there is to be any breakthrough for the undocumented in the US, Foreign Affairs Minister Charlie Flanagan has said.

After meeting with Mr Trump's National Security Adviser, General Michael Flynn, and his deputy, KT McFarland, at the White House, the minister said he had "sensitised" them to the mood of the Irish people.

"I directly conveyed to General Flynn the concern expressed in Ireland, and indeed, across the EU, at the most recent Executive Orders on immigration," Mr Flanagan told the AGM of the Irish Network Washington last night.

"In response, General Flynn outlined the rationale for this order while I pointed out its damaging consequences in humanitarian terms, as well as for the international reputation of the United States."

Mr Flynn is among the president's most controversial appointments. He's known for being combative and has a history of making provocative statements about Islam.

Various US media organisations have also criticised him for spreading misinformation, known as 'Flynn Facts' when he served as assistant director of national intelligence.

However, Mr Flanagan stressed his purpose in Washington was to engage with the White House and members of Congress.

"The political context in Washington may have changed, but the Irish Government's objectives remain constant - achieve some relief for the undocumented and find some legislative pathway for legal immigration," he said.

"There has been much written and said about the different tone and style of this new administration.

"But I want to emphasise that the unique relationship that exists between Ireland and the United States is as strong as ever.

"Whether one looks at the economic, political, cultural, or any other manifestation of the relationship, one can see the real depth of the ties that bind our two nations together."